1. Field of the Invention
The present invention relates to wrappers for smoking articles such as cigarettes and especially to such wrappers which reduce the tendency of cigarettes to cause ignition of surfaces which come in contact with the lit cigarette. Reports have been made of fires attributed to burning cigarettes coming in contact with combustible materials. Such reports have generated interest in reducing the tendency of cigarettes to ignite surfaces and materials included in furniture, bedding, and the like upon contact. One obviously desirable attribute of cigarettes in this regard would be that they extinguish themselves if left unattended for a period of time whether in an ash tray or in open air. Since it is recognized by those skilled in the art that the wrapper construction for the cigarette strongly influences the behavior of the cigarette during smolder, modification of the wrapper to achieve these desired results would be highly beneficial. In particular, a wrapper construction that does so without serious detrimental effects on desired smoking properties and characteristics would be especially advantageous. The present invention is directed to such wrapper constructions and improved smoking articles utilizing them.
2. Description of the Prior Art
The subject of reducing the tendency of cigarettes to ignite upholstery, bedding, and the like has received much attention.
Considerable effort has been directed to modifications of cigarette papers for the purpose of reducing fire hazards, including the development of non-burning wrappers, for example, as disclosed in U.S. Pat. No. 2,998,012 to Lamm dated Aug. 29, 1961, and the design of wrappers having patterned rings or areas of non-burning materials, for example, as disclosed in U.S. Pat. No. 4,044,778 to Cohn dated Aug. 30, 1977.
It is also known, as in U.S. Pat. No. 4,231,377 to Cline, for example, to treat conventional wrappers with chemical adjuvants such as alkali metal citrates to control burn properties.
It is, moreover, known as described in copending and coassigned U.S. patent application Ser. No. 334,120 filed Dec. 24, 1981, now U.S. Pat. No. 4,461,311 issued July 24, 1984 to Mathews, DeLucia and Mattina that the addition of extraordinary amounts of burn promotion additives to cigarette paper leads to a reduced emission, sidestream smoke. Cigarettes made with such papers normally would not have self-extinguishing properties, however.
Additionally, copending and coassigned U.S. patent application Ser. No. 627,710 filed July 11, 1984 describes wrapper constructions with specially designed paper structures that yield cigarettes that will self-extinguish when in contact with a surface, including many commonly encountered combustible surfaces. Such cigarettes, however, free burn continuously in air and do not self-extinguish under free burn conditions.
In summary, it remains desired to produce wrapper constructions for cigarettes and the like that would result in a cigarette reliably self-extinguishing in air after burning for a specified and controlled period of time. It is further desired to produce such wrapper constructions that accomplish this objective without significant deleterious effects on desired smoking properties.